Andrew Liszewski

When you're traveling and away from a reliable power source, conserving your laptop's battery is of the utmost importance. And knowing which of your USB accessories draws the most juice thanks to this simple $31 power meter—whether it's a wireless adapter, an external drive, or even your phone—will help you max out whatever battery life you've got left.

Working with USB 1, 2, or 3 devices, the power meter has four different modes letting you see a device's power draw in real time, the average amount of power it's using every second, or its maximum and minimum draw during the duration it's been plugged into your computer. There's no stat tracking or uploads to an online database, it's just a quick and dirty way to determine if that USB reading light, or recharging your compact shaver, is sucking more power than you realize.